Such diagrammatic relations are typically more or less sporadic in the lexicon, but in a morphological system they may be paramount. Typical examples of diagrammatic patterns are the specialization of certain phonemes or diacritic signs as (parts of) signantia for classes of signata, e.g. consonants for past tense morphemes ("-l-, -f-") [...].
- Andersen (2004), Pag. 401